DSP, Jalpaiguri Probhat Chakraborty said that the NIA team collected samples from the blast site.

“No one had been arrested or detained by the police till now,” he said.

The DSP, however, refused to comment when his attention was drawn to an SMS circulated purportedly by the Kamtapur Liberation Organization (KLO), suspected to have carried out the blast, denying its involvement.

"We won't say anything on this matter now. All angles to the blast are being investigated," Chakraborty said.

A senior police official, however, noted that it needed to be explored whether it was a pre-planned blast or an accidental one as some fairs were going on in the area.

IG, North Bengal Shashikant Pujari on Friday submitted a detailed report on the incident to the IG (law and order), Anuj Sharma.

On being asked if there was a prior intelligence alert about the blast, Anuj Sharma said, "As the KLO was observing its martyrs' day yesterday, we had issued a general alert requiring us to conduct checks at various check points."

On whether it was an intelligence or security failure, Sharma replied, "I won't say anything right now. The probe is on. The CID and IB are looking into the matter."

State Forensic teams and CID officials also reached the Jalpaiguri town on Friday to examine the kind of explosives used to carry out the blast, the police said.

The needle of the blast pointed to the KLO, an organization formed in 1993 to fight for a separate Kamtapuri state comprising six districts of North Bengal and some areas of Lower Assam.